Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          492        186 
1992          773        311 
1993         1663        608 
1994         2320        837 
1995         3368       1171 
1996         3576       1256 
1997         2326        793 
1998        23250       9803 
1999        14522       5568 
2000        40450      16784 
2001        43016      16680 
2002        32464      14511 
2003        61157      25356 
2004        47929      18382 
2005        85243      26210 
2006       110709      35376 
2007       203739      62492 
2008       124943      35565 
2009       101606      28557 
2010       118122      32812 
2011       177025      48957 
2012       164389      45454 
2013       254982      72121 
2014       604968     154903 
2015       730438     193704 
2016       708747     183026 
2017       600958     162124 
2018       395698     110868 
2019       929439     227946 
2020       691528     176902 
2021       893545     213888 
2022       663568     189794 
2023       602936     173570 
2024       244846      70890